Manufacture of billets for seamless tubes



March 10. 1925 S. E. DIESCHER MANUFACTURE OF BILLETS FOR SEAMLESS TUBES S v a p e n a ovcu a a v n a a n a pa p F/GU/IES 1 705 1 U5 73/1725 PRIOR ART JNVENTOR.

LPWM A T TORNEY.

March 10, 1925- 1,529,301

s. E. DIESCHER MANUFACTURE OF BILLETS FOR SEAMLESS 'iUBES Filed April 17, 1923 3 Sheets-Sheet 2 F1618, FIG. 9.

INVENTOR. W FIG .10.

March 10. 1925- S. E. DIESCHER IANUFACTURB OF BILLETS FOR SEAMLESS 'l'iJBES Filed April 17, 1923 3 Sheets-Sheet 3 INVENTOR.

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ATTURNEX Patented Mar. 10, 1925.

UNITED STATES 1,529,301 PATENT OFFICE.

SAMUEL E DIESCHER, 0F WILmNSBURG. PENNSYLVANIA, ASSIGNOR T0 S. DIESCHER 8c SONS, A PARTNERSHIP CONSISTING OF SAID SAMUEL E. DIESCHER AND AUGUST P. DIESCHER. OF PITTSBURGH, PENNSYLVANIA MANUFACTURE 01: BILLETS FOR SW5 TUBES.

Application filed April 17, 1923. Serial No. 632,684.

T 0 all whom it may concern:

Be it known that I, SAMUEL E. DIESCHER. residing at VVilkinshurg, in the county of Allegheny and State of Pennsylvania. a citizen of the United States, have invented or discovered certain new anduseful Improvements in Manufacture of Billets for Seamless Tubes. of which improvements the following is a specification.

In the accompanying drawings forming a part of thi: specification, the several views are merely diagrammatic. Figs. 1 to 5 inclusive illustrate the present practice eifecting the reduction of a rectangular ingot to a circular billet. and Figs 6 to 14 illustrate steps employed in the practice of the invention claimed herein.

It has been the general practice in the manufacture of seamless tubes in this country to reduce a rectangular ingot by rolling to a round billet having a diameter dependent on the size of the tube to be formed, pierce the billet, and then reduce the latter y rolling to the required cross section. As is well known, the metal is subjected while being pierced to very severe transverse strains which not infrequently result in splitting the billet. Foreign manufacturers avoided this difliculty by resorting to the practice of casting ingots having dimensions suitable for piercing without any previous reduction. This method is objectionable under conditions prevailing in this country, on account of the large number of molds required, and the time and labor consumed, and the variety of sizes of small ingots which must be kept on hand, and the consequent expense involved.

It is well known to those skilled in the art that the metal of the central portion of cast steel ingots is of much poorer quality than the outer portions, and contains impurities. This condition is due in part to the contraction of the metal in cooling. and in part to the segregation of impurities. Cooling and solidification proceeds inwardly and in the construction resulting from cooling. the metal in the center is pulled outwardly so that the central portion of the ingot is less dense than the outer portions. And further, during cooling, impurities move inwardly towards the axis thereby increasing the percentage of impurities in the central portion of the ingots,

all tending towards the poorer quality of material in the central portion of the ingot brought about by the solidification of the metal as hereinbefore stated. This portion of the ingot containing the poorer quality of material will be hereinafter referred to as the core.

It has been ascertained by me that the transverse shape of the core, whether due to contraction or the presence of impurities, corresponds to the transverse shape of the mold in which the steel is cast and solidifies, as for example, when rectangular molds are employed, that the core will be rectangular in cross section, and if the shell be ctist in a mold circular in cross-section, the core will be circular. It has also been ascertained that when an ingot is reduced by rolling to a round, such as is employed in the manufacture of seamless tubes, the core will be proportionately reduced in cross'sectional area, but its transverse shape will not he changed.

When an ingot is formed in a rectangular mold, as indicated in Fig. 1 which is the general practice, the contraction of the material and movement of impurities inwardly will be dependent on the rate of cooling of the metal, and as the cooling will proceed with approximate uniformity from each of the four walls of the mold, the portion of the ingot forming the core will be substantially rectangular in cross section.

In reducin a rectangular ingot which is tape'red longitudinally it is first rolled on the fiat surfaces of blooming rolls, until its transverse dimensions are uniform through its entire length. It is then reduced until its rectangular cross sectional dimensions approach those desired in the finished article. the last pass in such reduction being what is known as a box pass, as shown in Fig. 2. While being reduced from the ingot to suit.- able dimensions for reduction in the box pass, the ingot or bloom is frequently turned axially, ninety degrees. so that although the core will be given an oblong shape in some passes, it wil be restored to square shape when the article is turned ninety de rees, and further reduced. In other worcfs. in some passes the core will be reduced laterally in one direction and' when turned ninety degrees, will be reduced laterally in a direction at right angles to the reductio in a previous pass, and will have a substantially square shape as the article comes from the box pass. Further reduction to the desired round is effected in most cases by diamond, oval and round passes, as shown in Fig. 3, Fig. 4, and Fig. 5. Intermediate the box and diamond passes, the article is axially turned forty-five degrees, so that in this pass two diametrically opposite corners a of the article will be rounded but the crosssectional contour of the other portions of the bloom will not be materially changed. Reduction is next effected in an oval pass (see Fig. 4), but prior to entering the oval pass, the article is turned axially ninety degrees so that the longer diameter of the article reduced in the diamond pass will be at right angles to the axes of the rolls having the oval pass. In this oval pass the metal will fiow not only longitudinally, but also laterally, from the corners 0 into the adjacent sides, but as the flow of metal is proportional to the distance from the axis of the article. there will be a greater change in form in the shell 1 than in the core, and hence the thickness of the shell in line with the corners or will be reduced.

After reduction in the oval pass, the article is turned axially ninety degrees and fed into the circular pass (see Fig. 5). In this pass the corners a of the article are operated on, the principal flow of metal being longitudinal. There will be some lateral flow in both directions from the corners a, and by reason of such lateral flow the thickness of the shell at the corners a will be reduced.

It will be readily understood by those skilled in the art that. as the thickness of the shell 1 in line with the corners of the core, is reduced in the passes wherein the article is changed from a square to a round. there will be four lines of relative weakness as against transverse strains, extending longitudinally of the round. Hence. when piercing the round in which operation the metal is subject to very great transverse strains. the billet is frequently split lon itudinally, the split occuring in line with t e corners of the core.

In the practice of the invention claimed herein, advantage is taken of the influence which the transverse shape of the mold has on the transverse shape of the core or portion containing the poorer metal, and the ingot is cast in amold circular in cross-section. In these circular molds, solidification and contraction and also the movement of impurities will be at a substantially uniform rate from all oints of the inner surface of the mold, an hence there will be formed a. core 3 circular in cross section enclosed in the shell 4 of clean and practically homogenous metal, as indicated in Fig. 6.

The ingot which is circular in cross-section and also tapering from end to end, is reduced by rolling on the flat surfaces of the rolls of the blooming mill to a bloom square for its entire length, as shown in Fig. 9. The bloom is then reduced in the same manner as described before for reduction of ingots of rectangular cross-section until its cross-sectional dimensions are suitable to permit its reduction in the box pass shown in Fig. 11.

In reducing the ingot from a circular shape to a square, it will be turned ninety degrees intermediate its several reductions, hence although the core may be given an approximately oval sha we in one pass, the reduction in a succeeding pass after being turned ninety degrees. will effect a restoration of the core to a circular shape. The reduction effected in the box pass will bring the article nearly to the cross-sectional area desired in the finished billet, and reduction is effected in the diamond. oval. and circular passes shown in Figs. 12, 13 and 14, to transform the square shape as it leaves the box pass to a round billet.

Before the article is fed to the diamond pass (see. Fig. 12) it is turned axially through an arc of forty five degrees so that one of the diagonals of the square will be at right angles to the axes of the rolls, and reduction in this pass will be at the corners d which are rounded. The article is next reduced in the oval pass (see Fig. 13) but before being entered in such pass, it is axially turned ninety degrees. This oval pass is. designed so that reduction will be effected almost wholly at the corners 6, some of the metal flowing longitudinally resulting in elongation of the article and a portion of the displaced metal flowing laterall in both directions from the corners e, tend ing to widen the oval as shown in full lines, and due to this lateral flow, the previously rounded corners d are forced outward increasing the diameter of the article and core parallel with the axis of the rolls. The cross sectional area of the core is reduced. and its contour made oval having its shorter diameter coincident with a line passing through the corners c. This shorter diameter fof the core of the article as it comes from the oval ass will be approximately equal to the diameter of the core in the finished article.

Following reduction in the oval pass, the article is turned axially ninety degrees and fed to the circular pass (Fig. 14). In turning the article ninet degrees. the longer diameter of the artic e and also of the core will be at right angles to the axes of the rolls so that in said circular pass the oval is transformed to a round, an this is true not only of the article itself but also of the core.

It is characteristic of the method described herein that although reduction of the ingot is effected for the most part in a. succession of square or rectangular cross-sections of diminishing areas, there will not be any such change in the contour of the core in any of the rectangular forms that cannot be and will not be corrected in subsequent reduction to square cross sections and in the final passes brought to the same contour as the cross section of the article itself, whichis circulan It will be observed by reference to Figs. 7, 8, 9, and 10 that the thickness of the shell 4 of clean metal is greater in line with the corners of the article than at the sides, and that by reduction in the oval and circular passes, the shell has finally a uniform thickness.

It will be understood that when reducing the ingot shown in Fig. 6 which is shown as a true circle, the core will be flattened in one pass and restored to original contour when the article is turned axially for reduction in the next pass and so on to the last pass. It will be readily understood by those skilled in the art that if the ingot were cast in an oval or elliptical mold the contour. of the core would be oval or elliptical, and during reduction the oval core would be changed to or approximately to a true circle and then to an oval, and in the resultant billet the contour of the core would be approximately a true circle provided the bloom were so fed to the box pass that the core of the article emerging therefrom would have a contour approximately a true circle. Hence the claims should be construed as covering an ingot the periphery of which is curved.

I claim herein as my invention:

1. The method herein described of manu- 4 facturing round billets which consists in forming an ingot haxing a curved periphery and reducing such ingot by rolling to a round billet between rolls having their axes in vertical planes at right angles to the axis of the billet.

2. The method herein described of manufacturing round billets which consists in casting an ingot having a curved peripher reducing such ingot to a bloom rectangular in cross-section, and rolling such bloom down to a billet circular in cross section.

In testimony whereof, I have hereunto set my hand.

SAMUEL E. DIESCHER. 

